1. Field of the Invention
The present disclosure relates to a method for fabricating liquid crystal displays; and, more particularly, to a method for fabricating an active matrix liquid crystal display (hereinafter referred to as “AM LCD”) and a passive matrix liquid crystal display (hereinafter referred to as “PM LCD”) based on a plastic film substrate.
2. Background of the Related Art
Liquid crystal displays (hereinafter referred to as “LCDs”) based on glass substrates were first introduced in the early sixties, and have been widely adopted as information displays in everyday electronics, for example, calculators, watches, cellular phones, PDAs, audio and video equipments, computers, car dashboards, and the like. These LCDs based on glass substrates, despite their widespread uses, are not without problems, the problems being all related to the inherent properties of the glass substrates. For example, these LCDs are not resistant to shock, relatively heavy, are not bendable, and the thickness thereof is limited by the thickness of the glass substrate used. One obvious solution to such problems is to replace the glass substrates with appropriate plastic film substrates.
FIGS. 1a through 1c are cross-sectional views illustrating a prior art method for manufacturing a liquid crystal display using a plastic film substrate as disclosed in Pub. No. U.S. 2003/0123019.
Referring to FIG. 1a and FIG. 1b, a plastic film substrate 20 is arranged and fixed onto a subsidiary substrate 60 made of a glass through a heat resistant fixing tape 70 placed between the plastic film substrate 20 and the subsidiary substrate 60 along the circumferences thereof. The subsidiary substrate 60 is further fixed onto a processing table 10 by vacuum pressure. An alignment layer 40 for controlling the initial alignment of liquid crystals is then formed on top of the plastic film substrate 20 by first coating an alignment material using an off-set printing method, and rubbing the alignment material with a rubbing rag 50 as shown in FIG. 1b, resulting in a lower plastic substrate 100 as shown in FIG. 1c. A corresponding upper plastic substrate 200 is formed using the processes described above.
A liquid crystal cell is formed between the lower and upper plastic substrates 100 and 200 by facing the lower and upper substrates 100 and 200 at a distance, i.e., cell gap, and partially joining them together with a sealant 30. Subsequently, the fixing tapes 70 on the lower and upper plastic substrates 100 and 200 are removed therefrom and then divided to form liquid crystal cells. These cells are filled up with appropriate liquid crystals to form liquid crystal displays.
In the above-mentioned prior art method for fabricating a LCD with a plastic film substrate, there exist a number of shortcomings. For example, since only circumference of plastic film substrate is glued onto the subsidiary substrate using the heat resistant fixing tape, the plastic film substrate may become unintentionally detached during the manufacturing process and may get damaged by the fixing tape during the detaching process. Further, as shown in FIG. 1c, in order for the processes described above to work, steps must be created on the plastic film substrate along the edge thereof, and this, considering the thickness of the plastic substrate, is extremely difficult and hence costly. In addition, air bubbles may form between the plastic film substrate and the subsidiary substrate, detrimentally affecting the yield and the cost. Finally, the divided subsidiary substrates are not allowed to be reused, increasing the overall manufacturing cost.